Friction materials that are used for the disc-brake pads used in the brakes of two-wheeled vehicles or four-wheeled vehicles, electromagnetic brakes and industrial brakes, are required to be acceptable in terms of characteristics such as effectiveness, abrasion resistance, brake noise, and judder which is a forced vibration resulting from a thickness deviation in the rotor.
Particularly, brake noise characteristic is important in connection with the comfortability of brakes. In order to ameliorate brake noise, it is effective to enhance the damping properties (tan δ) of the friction material used in the brakes. Therefore, it has been proposed to enhance the damping properties of a friction material by a method of softening the resin used as a binding material by using an acrylic elastomer and a nitrile rubber; a method of adding a rubber powder, cashew dust and the like as a material of a friction adjusting material to decrease the elastic modulus of the friction material; and the like (see, for example, Patent Literatures 1 and 2).